As a common protective structure in underground engineering

reinforced concrete (Reinforced Concrete，RC) arches are seriously threatened by thermobaric weapons

and the damage effects remain unclear. Through conducting close-in explosion tests of the RC arch with thermostatic explosives

the failure patterns of RC arches are clarified. A numerical model based on the Miller model in the finite element method is established

incorporating the afterburning effect of thermobaric explosives. This model's accuracy is verified by comparing it with experimental data. Systematic studies investigate the damage characteristics and destruction pattern of RC arches under different charge masses and explosion distances

clarifying the damage modes of the arch. A method for assessing damage degree based on changes in the deflection angle between the vault and the arch waist is proposed. Results indicate that close-range thermobaric explosions cause four main damage modes: arch vault cracking

concrete collapse and peeling on the back explosion surface

combination of global bending failure and local penetration failure

and severe collapse failure. Larger charges and higher explosion distances lead to more significant overall damage. As the explosion distance decreases

structural damage tends towards localized penetration failure. Damage degree prediction method based on charge mass and standoff distance (W-R) is developed

which can effectively assess the damage degree of RC arches subjected to close-in thermobaric explosions.